Hormonal contraception refers to birth control methods that act on the endocrine system. Almost all methods are composed of steroid hormones, although in India one selective estrogen receptor modulator is marketed as a contraceptive. The original hormonal method—the combined oral contraceptive pill—was first marketed as a contraceptive in 1960. In the ensuing decades many other delivery methods have been developed, although the oral and injectable methods are by far the most popular. Altogether, 18% of the world's contraceptive users rely on hormonal methods. Hormonal contraception is highly effective: when taken on the prescribed schedule, users of steroid hormone methods experience pregnancy rates of less than 1% per year. Perfect-use pregnancy rates for most hormonal contraceptives are usually around the 0.3% rate or less. Currently available methods can only be used by women; the development of a male hormonal contraceptive is an active research area.
There are two main types of hormonal contraceptive formulations: combined methods which contain both an estrogen and a progestin, and progestogen-only methods which contain only progesterone or one of its synthetic analogues (progestins). Combined methods work by suppressing ovulation and thickening cervical mucus; while progestogen-only methods reduce the frequency of ovulation, most of them rely more heavily on changes in cervical mucus. The incidence of certain side effects is different for the different formulations: for example, breakthrough bleeding is much more common with progestogen-only methods. Certain serious complications occasionally caused by estrogen-containing contraceptives are not believed to be caused by progestogen-only formulations: deep vein thrombosis is one example of this.
Birth control, also known as contraception and fertility control, are methods or devices used to prevent pregnancy. Planning, provision and use of birth control is called family planning. Safe sex, such as the use of male or female condoms, can also help prevent sexually transmitted infections. Birth control methods have been used since ancient times, but effective and safe methods only became available in the 20th century. Some cultures deliberately limit access to birth control because they consider it to be morally or politically undesirable.
The most effective methods of birth control are sterilization by means of vasectomy in males (99.95% success rate) and tubal ligation in females (99.5% success rate), intrauterine devices (IUDs) and implantable contraceptives. This is followed by a number of hormonal contraceptives including oral pills, patches, vaginal rings, and injections. Less effective methods include barriers such as condoms, diaphragms and contraceptive sponge and fertility awareness methods. The least effective methods are spermicides and withdrawal by the male before ejaculation. Sterilization, while highly effective, is not usually reversible; all other methods are reversible, most immediately upon stopping them. Emergency contraceptives can prevent pregnancy in the few days after unprotected sex. Some regard sexual abstinence as birth control, but abstinence-only sex education may increase teen pregnancies when offered without contraceptive education.
The combined oral contraceptive pill (COCP), often referred to as the birth-control pill or colloquially as "the Pill", is a birth control method that includes a combination of an estrogen (estradiol) and a progestogen (progestin). When taken by mouth every day, these pills inhibit female fertility. They were first approved for contraceptive use in the United States in 1960, and are a very popular form of birth control. They are currently used by more than 100 million women worldwide and by almost 12 million women in the United States. Use varies widely by country, age, education, and marital status: one third of women aged 16–49 in the United Kingdom currently use either the combined pill or a progestogen-only "minipill", compared to only 1% of women in Japan.
Combined oral contraceptive pills should be taken at the same time each day. If one or more tablets are forgotten for more than 12 hours, contraceptive protection will be reduced. Most brands of combined pills are packaged in one of two different packet sizes, with days marked off for a 28 day cycle. For the 21-pill packet, a pill is consumed daily for three weeks, followed by a week of no pills. For the 28-pill packet, 21 pills are taken, followed by week of placebo or sugar pills. A woman on the pill will have a withdrawal bleed sometime during the placebo week, and is still protected from pregnancy during this week. There are also two newer combination birth control pills (Yaz 28 and Loestrin 24 Fe) that have 24 days of active hormone pills, followed by 4 days of placebo.